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System:TriclinicColour:Colorless to pale pink; ...
Name:Named in 2013 by M. M. Haring and Andrew M. McDonald in honor of Anthony Hosford Steede, dedicated mineral collector and specialist in the minerals of Mont Saint-Hilaire, Quebec, Canada.

Closely related to the sérandite-pectolite series of the pyroxenoid group and is the first mineral found to contain single loop-branched dreier silicate chains.

Classification of Steedeite

IMA status:Approved 2013
Explanation of status:A different material was originally approved as a new mineral (IMA 2010-049), but the approval was later withdrawn in October 2011 since further investigations had shown that the mineral is identical to catapleiite.

Subsequently a different mineral was submitted as IMA2013-052.
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Type Occurrence of Steedeite

Type Locality:Poudrette quarry (Demix quarry; Uni-Mix quarry; Desourdy quarry; Carrière Mont Saint-Hilaire), Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie, Québec, Canada
General Appearance of Type Material:Bundles of slightly radiating acicular crystals to 0.5 mm.
Place of Conservation of Type Material:Type material is deposited in the collections of the Royal Ontario Museum, Queen’s Park, Toronto, Ontario, Canada, catalogue number M56489
Geological Setting of type material:Late-stage mineral in sodalite syenite
Associated Minerals at type locality:
MicroclineEudialyte GroupCatapleiiteAnalcimeAegirine

Physical Properties of Steedeite

Lustre:Sub-Vitreous, Silky
Diaphaneity (Transparency):Transparent, Translucent
Colour:Colorless to pale pink; white
Cleavage:None Observed
Density (calculated):3.106 g/cm3

Crystallography of Steedeite

Crystal System:Triclinic
Class (H-M):1 - Pinacoidal
Space Group:P1
Space Group Setting:P1
Cell Parameters:a = 6.837(1) Å, b = 7.575(2) Å, c = 8.841(2) Å
α = 99.91(3)°, β = 102.19(3)°, γ = 102.78 (2)°
Ratio:a:b:c = 0.903 : 1 : 1.167
Unit Cell Volume:V 424.81 ų (Calculated from Unit Cell)
Morphology:Acicular crystals.
X-Ray Powder Diffraction:

Optical Data of Steedeite


Chemical Properties of Steedeite

Simplified for copy/paste:NaMn2[Si3BO9](OH)2
Essential elements:B, H, Mn, Na, O, Si
All elements listed in formula:B, H, Mn, Na, O, Si

Other Names for Steedeite

Other Languages:

Other Information

Fluorescence in UV light:Weak pale green to pale yellow fluorescence under medium-wave radiation
Health Warning:No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Steedeite

Reference List:

- +
Haring, M.M. and McDonald, A.M. (2013) Steedeite, IMA 2013-052. CNMNC Newsletter No. 17, October 2013, page 3002; Mineralogical Magazine, 77, 2997-3005.

Haring, M.M.M. & McDonald A.M. (2014): Steedeite, NaMn2[Si3BO9](OH)2: Characterization, crystal-structure determination, and origin. Canadian Mineralogist, 52, 47-60.

Internet Links for Steedeite

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  • Raman and XRD data at RRUFF project
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  • Localities for Steedeite

    The map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
    (TL) indicates type locality. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
    • Québec
      • Montérégie
        • La Vallée-du-Richelieu RCM
          • Mont Saint-Hilaire
    Haring, M.M. and McDonald, A.M. (2013) Steedeite, IMA 2013-052. CNMNC Newsletter No. 17, October 2013, page 3002; Mineralogical Magazine, 77, 2997-3005.
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